Efficient transmission for low data rate WLAN

ABSTRACT

A fragmentation threshold is dynamically determined based on a current transmission rate. A medium access control (MAC) service data unit (MSDU) is received, and it is determined whether a length of the MSDU exceeds the fragmentation threshold. The MSDU is fragmented into multiple MAC protocol data units (MPDUs) when it is determined that the length of the MSDU exceeds the fragmentation threshold, whereas an MPDU that includes the MSDU is generated when it is determined that the length of the MSDU does not exceed the fragmentation threshold.

CROSS-REFERENCES TO RELATED APPLICATIONS

This disclosure is a divisional application of U.S. application Ser. No.13/492,538, entitled “EFFICIENT TRANSMISSION FOR LOW DATA RATE WLAN,”filed Jun. 8, 2012 (now U.S. Pat. No. 8,088,908), which claims thebenefit of the following U.S. Provisional patent applications:

-   -   U.S. Provisional Patent Application No. 61/494,609, entitled        “802.11ah Very Low Rate Support,” filed on Jun. 8, 2011;    -   U.S. Provisional Patent Application No. 61/501,136, entitled        “802.11ah Very Low Rate Support,” filed on Jun. 24, 2011;    -   U.S. Provisional Patent Application No. 61/521,217, entitled        “802.11ah Very Low Rate Support,” filed on Aug. 8, 2011;    -   U.S. Provisional Patent Application No. 61/560,715, entitled        “802.11ah Very Low Rate Support,” filed on Nov. 16, 2011;    -   U.S. Provisional Patent Application No. 61/588,852, entitled        “802.11ah Very Low Rate Support,” filed on Jan. 20, 2012; and    -   U.S. Provisional Patent Application No. 61/622,790, entitled        “Short Beacon Format—H.2.0 Info,” filed on Apr. 11, 2012;

The disclosures of all of the above-referenced patent applications arehereby incorporated by reference herein in their entireties.

This disclosure is also related to the following U.S. patentapplications, filed on the same day as the parent application:

-   -   U.S. patent application Ser. No. 13/492,452, entitled “EFFICIENT        TRANSMISSION FOR LOW DATA RATE WLAN” (now U.S. Pat. No.        8,995,367);    -   U.S. patent application Ser. No. 13/492,572, entitled “EFFICIENT        TRANSMISSION FOR LOW DATA RATE WLAN” (now U.S. Pat. No.        9,019,914); and    -   U.S. patent application Ser. No. 13/492,522, entitled “EFFICIENT        TRANSMISSION FOR LOW DATA RATE WLAN” (now U.S. Pat. No.        8,867,467).

The disclosures of all of the above-referenced patent applications arehereby incorporated by reference herein in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and,more particularly, to data unit formats for long range wireless localarea networks.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

When operating in an infrastructure mode, wireless local area networks(WLANs) typically include an access point (AP) and one or more clientstations. WLANs have evolved rapidly over the past decade. Developmentof WLAN standards such as the Institute for Electrical and ElectronicsEngineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards hasimproved single-user peak data throughput. For example, the IEEE 802.11bStandard specifies a single-user peak throughput of 11 megabits persecond (Mbps), the IEEE 802.11a and 802.11g Standards specify asingle-user peak throughput of 54 Mbps, the IEEE 802.11n Standardspecifies a single-user peak throughput of 600 Mbps, and the IEEE802.11ac Standard specifies a single-user peak throughput in thegigabits per second (Gbps) range.

Work has begun on two new standards, IEEE 802.11ah and IEEE 802.11af,each of which will specify wireless network operation in sub-1 GHzfrequencies. Lower frequency communication channels are generallycharacterized by better propagation qualities and extended propagationranges compared to transmission at higher frequencies. In the past,sub-1 GHz ranges have not been utilized for wireless communicationnetworks because such frequencies were reserved for other applications(e.g., licensed TV frequency bands, radio frequency band, etc.). Thereare few frequency bands in the sub 1-GHz range that remain unlicensed,with different specific unlicensed frequencies in different geographicalregions. The IEEE 802.11ah Standard will specify wireless operation inavailable unlicensed sub-1 GHz frequency bands. The IEEE 802.11afStandard will specify wireless operation in TV White Space (TVWS), i.e.,unused TV channels in sub-1 GHz frequency bands.

SUMMARY

In an embodiment, a method includes generating, at a network interface,a signal field that includes (i) a field to indicate that a physicallayer (PHY) data unit is a control frame, one or more of a frame controlfield, a receiver address (RA) field, and a cyclic redundancy check(CRC) field. The method also includes generating, at the networkinterface, a PHY data payload (i) that includes one or more of a servicefield, a transmitter address (TA) field, a network ID field, and a CRCfield, and (ii) that omits an RA field. The method additionally includesgenerating, at the network interface, the PHY data unit to include (i) apreamble, (ii) a PHY header having the SIG field, and (iii) the PHY datapayload, and transmitting, with the network interface, the PHY data unitor causing, with the network interface, the PHY data unit to betransmitted.

In other embodiments, the method further includes any combination of oneor more of the following elements.

The network ID field of the PHY data payload is a second network IDfield, and generating the signal field includes generating the signalfield to include a first network ID field.

The first network ID field includes a first portion of a basic serviceset identifier (BSSID), and the second network ID field includes asecond portion of the BSSID.

The first network ID field includes a first portion of a shortened orcompressed basic service set identifier (BSSID), and the second networkID field includes a second portion of the shortened or compressed BSSID.

Generating the signal field includes generating the signal field toinclude a service field, and generating the PHY data payload to omit theservice field.

In another embodiment, an apparatus comprises a network interfaceconfigured to generate a signal field that includes (i) a field toindicate that a physical layer (PHY) data unit is a control frame, and(ii) one or more of a frame control field, a receiver address (RA)field, and a cyclic redundancy check (CRC) field, and generate a PHYdata payload (i) that includes one or more of a service field, atransmitter address (TA) field, a network ID field, and a CRC field and(ii) that omits an RA field. The network interface is also configured togenerate the PHY data unit to include (i) a preamble, (ii) a PHY headerhaving the SIG field, and (iii) the PHY data payload, and transmit thePHY data unit or cause the PHY data unit to be transmitted.

In other embodiments, the apparatus further includes any combination ofone or more of the following elements.

The network ID field of the PHY data payload is a second network IDfield, and the network interface is configured to generate the signalfield to include a first network ID field.

The first network ID field includes a first portion of a basic serviceset identifier (BSSID), and the second network ID field includes asecond portion of the BSSID.

The first network ID field includes a first portion of a shortened orcompressed basic service set identifier (BSSID), and the second networkID field includes a second portion of the shortened or compressed BSSID.

The network interface is configured to generate the signal fieldincludes generating the signal field to include a service field, andgenerate the PHY data payload to omit the service field.

In yet another embodiment, a method includes dynamically determining, ata network interface, a fragmentation threshold based on a currenttransmission rate. The method also includes receiving a medium accesscontrol (MAC) service data unit (MSDU), and determining, at the networkinterface, whether a length of the MSDU exceeds the fragmentationthreshold. The method also includes fragmenting, at the networkinterface, the MSDU into multiple MAC protocol data units (MPDUs) whenit is determined that the length of the MSDU exceeds the fragmentationthreshold, and generating, at the network interface, an MPDU thatincludes the MSDU when it is determined that the length of the MSDU doesnot exceed the fragmentation threshold.

In still another embodiment, an apparatus comprises a network interfaceconfigured to dynamically determine a fragmentation threshold based on acurrent transmission rate, determine whether a length of a medium accesscontrol (MAC) service data unit (MSDU) exceeds the fragmentationthreshold, fragment the MSDU into multiple MAC protocol data units(MPDUs) when it is determined that the length of the MSDU exceeds thefragmentation threshold, and generate an MPDU that includes the MSDUwhen it is determined that the length of the MSDU does not exceed thefragmentation threshold.

In yet another embodiment, a method includes receiving a medium accesscontrol (MAC) service data unit (MSDU), and determining, at a networkinterface, whether a length of the MSDU exceeds a fragmentationthreshold. Additionally, the method includes fragmenting, at the networkinterface, the MSDU into multiple MAC protocol data units (MPDUs) whenit is determined that the length of the MSDU exceeds the fragmentationthreshold, and aggregating, at the network interface, a plurality of theMPDUs corresponding to the MSDU into an aggregate MPDU (A-MPDU).

In still another embodiment, an apparatus comprises a network interfaceconfigured to determine whether a length of a medium access control(MAC) service data unit (MSDU) exceeds a fragmentation threshold,fragment the MSDU into multiple MAC protocol data units (MPDUs) when itis determined that the length of the MSDU exceeds the fragmentationthreshold, and aggregate a plurality of the MPDUs corresponding to theMSDU into an aggregate MPDU (A-MPDU).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example wireless local area network(WLAN) 10, according to an embodiment.

FIG. 2 is a diagram of an example media access control (MAC) layerfragmentation operation, according to an embodiment.

FIG. 3 is a flow diagram of an example method for determining whether aMAC service data unit (MSDU) should be fragmented and fragmenting theMSDU when appropriate, according to another embodiment.

FIG. 4 is a flow diagram of another example method for determiningwhether an MSDU should be fragmented and fragmenting the MSDU whenappropriate, according to another embodiment.

FIG. 5 is a diagram of another example MAC layer fragmentationoperation, according to another embodiment.

FIG. 6 is a flow diagram of an example method for fragmenting an MSDU,when appropriate, and aggregating multiple MSDU fragments into anaggregate MAC protocol data unit (A-MPDU), when appropriate, accordingto an embodiment.

FIG. 7A is a diagram of an example MSDU fragment included in an A-MPDUand that may be utilized for at least some MSDU fragments in an A-MPDU,in an embodiment.

FIG. 7B is a diagram of an example A-MPDU subframe, which includes anMSDU fragment, according to an embodiment.

FIG. 8 is a diagram of an example fragmentation/aggregation operation,according to an embodiment.

FIG. 9A is a diagram of an example extended physical layer (PHY)protocol data unit (PPDU), according to an embodiment.

FIG. 9B is a diagram of another example extended PPDU, according toanother embodiment.

FIG. 10 is a flow diagram of an example method for fragmentation andsubsequent aggregation, according to an embodiment.

FIG. 11 is a flow diagram of an example method for formatting data unitsfor wireless transmission, according to an embodiment.

FIG. 12 is a flow diagram of an example method for formatting data unitsfor wireless transmission, according to an embodiment.

FIG. 13 is a flow diagram of an example method for generating PPDUs,according to an embodiment.

FIG. 14 is a diagram of a PPDU format, according to an embodiment.

FIG. 15 is a flow diagram of an example method for generating a PHY dataunit, according to an embodiment.

FIG. 16 is a diagram of an example beacon frame, according to anembodiment.

FIG. 17 is a diagram of another example beacon frame, according toanother embodiment.

FIG. 18 is a diagram of another example beacon frame, according toanother embodiment.

FIG. 19 is a diagram of another example beacon frame, according toanother embodiment.

FIG. 20 is a diagram of another example beacon frame, according toanother embodiment.

FIG. 21 is a diagram of another example beacon frame, according toanother embodiment.

FIG. 22 is a diagram of another example beacon frame, according toanother embodiment.

FIG. 23 is a diagram of another example beacon frame, according toanother embodiment.

FIG. 24 is a diagram of an example control frame that omits a PHYpayload, according to an embodiment.

FIG. 25 is a flow diagram of an example method for generating a controlframe that omits a PHY payload, according to an embodiment.

FIG. 26 is a diagram of an example shortened control frame, according toan embodiment.

FIG. 27 is a flow diagram of an example method for generating ashortened control frame, according to an embodiment.

DETAILED DESCRIPTION

In embodiments described below, a wireless network device such as anaccess point (AP) of a wireless local area network (WLAN) transmits datastreams to one or more client stations. The AP is configured to operatewith client stations according to at least a communication protocol. Inan embodiment, the communication protocol defines operation in a sub 1GHz frequency range, and is typically used for applications requiringlong range wireless communication with relatively low data rates (e.g.,as compared to the communication protocol defined by the IEEE 802.11nStandard). The communication protocol (e.g., as defined by the IEEE802.11af Standard or the IEEE 802.11ah Standard, currently indevelopment, in some embodiments) is referred to herein as a “longrange” communication protocol.

In an embodiment, the long range communication protocol defines two ormore communication modes including at least a regular mode and a verylow rate (VLR) mode. The VLR mode has lower data rates than the regularmode and is intended for communication at even longer ranges as comparedwith the regular mode.

The current IEEE 802.11 Standard defines a maximum physical layer (PHY)protocol data unit (PPDU) duration of approximately 5 milliseconds (ms).At some of the data rates being proposed for the IEEE 802.11af and802.11ah Standards, the amount of data capable of being transmittedwithin 5 ms is relatively low, resulting in relatively high overhead andrelatively low efficiency. For example, using some of the data ratesbeing proposed for the IEEE 802.11af and 802.11ah Standards and with amaximum PPDU duration of 5 ms, excessive fragmentation of media accesscontrol (MAC) data units may occur. Table 1 lists example PPDU payloadsizes for the lowest data rate, at various channel bandwidths, beingcontemplated for the IEEE 802.11af and 802.11ah Standards.

TABLE 1 Maximum Size of PPDU Channel Bandwidth (MHz) Data Rate (Mbps)Payload (bytes) 20 6 3720 10 3 1755 5 1.5 877.5 2.5 0.75 438.75 1.250.375 219.375

As can be seen in Table 1, in some situations, the PPDU may only becapable of carrying at most approximately 200 bytes. When consideringthat an Ethernet frame can be as long as 1500 bytes, a high number ofMAC data units may need to be fragmented in at least some scenarios.Additionally, because each MAC data unit fragment includes MAC headerinformation, the MAC layer efficiency (the percentage of payload datathat is being transmitted when taking into account MAC header data)decreases as the data rate decreases.

One potential option is to increase the maximum PPDU duration. Table 2lists example MAC layer efficiencies for different PPDU durations for adata rate being contemplated for the IEEE 802.11af and 802.11ahStandards.

TABLE 2 Data Rate MSDU MAC Layer PPDU Duration (Mbps) (bytes) ThroughputEfficiency  5 ms 0.1875 45 0.044920783 23.96% 10 ms 0.1875 1620.099620384 53.13% 15 ms 0.1875 280 0.124032942 66.15% 20 ms 0.1875 3970.137859144 73.52%

As can be seen in Table 2, increasing the maximum PPDU durationincreases MAC layer efficiency. On the other hand, extending the maximumPPDU duration beyond 5 ms leads to longer medium sensing times forchannel access (which may increase power consumption because devices mayneed to spend more time awake), and is problematic because time varyingchannel conditions can adversely affect reception of the latter end of avery long PPDU.

In some embodiments described below, techniques for reducingfragmentation are utilized. Also, in some embodiments described below,techniques for reducing protocol overhead when fragmentation occurs areutilized. Additionally, in some embodiments described below, techniquesare utilized for improving operation when extended length PPDUs aretransmitted.

FIG. 1 is a block diagram of an example wireless local area network(WLAN) 10, according to an embodiment. An AP 14 includes a hostprocessor 15 coupled to a network interface 16. The network interface 16includes a medium access control (MAC) processing unit 18 and a physicallayer (PHY) processing unit 20. The PHY processing unit 20 includes aplurality of transceivers 21, and the transceivers 21 are coupled to aplurality of antennas 24. Although three transceivers 21 and threeantennas 24 are illustrated in FIG. 1, the AP 14 can include differentnumbers (e.g., 1, 2, 4, 5, etc.) of transceivers 21 and antennas 24 inother embodiments.

The WLAN 10 includes a plurality of client stations 25. Although fourclient stations 25 are illustrated in FIG. 1, the WLAN 10 can includedifferent numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations 25 invarious scenarios and embodiments. At least one of the client stations25 (e.g., client station 25-1) is configured to operate at leastaccording to the long range communication protocol.

The client station 25-1 includes a host processor 26 coupled to anetwork interface 27. The network interface 27 includes a MAC processingunit 28 and a PHY processing unit 29. The PHY processing unit 29includes a plurality of transceivers 30, and the transceivers 30 arecoupled to a plurality of antennas 34. Although three transceivers 30and three antennas 34 are illustrated in FIG. 1, the client station 25-1can include different numbers (e.g., 1, 2, 4, 5, etc.) of transceivers30 and antennas 34 in other embodiments.

In an embodiment, one or more of the client stations 25-2, 25-3 and25-4, has a structure the same as or similar to the client station 25-1.In these embodiments, the client stations 25 structured the same as orsimilar to the client station 25-1 have the same or a different numberof transceivers and antennas. For example, the client station 25-2 hasonly two transceivers and two antennas, according to an embodiment.

In various embodiments, the PHY processing unit 20 of the AP 14 isconfigured to generate data units conforming to the long rangecommunication protocol and having formats described hereinafter. Thetransceiver(s) 21 is/are configured to transmit the generated data unitsvia the antenna(s) 24. Similarly, the transceiver(s) 24 is/areconfigured to receive the data units via the antenna(s) 24. The PHYprocessing unit 20 of the AP 14 is configured to process received dataunits conforming to the long range communication protocol and havingformats described hereinafter, according to various embodiments.

In various embodiments, the PHY processing unit 29 of the client device25-1 is configured to generate data units conforming to the long rangecommunication protocol and having formats described hereinafter. Thetransceiver(s) 30 is/are configured to transmit the generated data unitsvia the antenna(s) 34. Similarly, the transceiver(s) 30 is/areconfigured to receive data units via the antenna(s) 34. The PHYprocessing unit 29 of the client device 25-1 is configured to processreceived data units conforming to the long range communication protocoland having formats described hereinafter, according to variousembodiments.

In some embodiments, a network interface (e.g., the network interface 16of the AP 14 and/or the network interface 27 of the client station 25)is configured to operate in at least two modes including a regular modeand a VLR mode. For example, in an embodiment, the VLR mode utilizes aslower clock rate as compared to the regular mode. In an embodiment, thedifferent clock rates correspond to different data rates. Thus, the VLRmode generally corresponds to slower data rates as compared to theregular mode, at least for some modulation coding schemes (MCSs).

In another embodiment, a PHY data unit generated for the VLR mode isgenerated using the same clock rate used to generate a regular mode PHYdata unit, but using a Fast Fourier Transform (FFT) of a smaller sizecompared to the FFT size used to generate the data unit for a regularmode. In such embodiments, the smaller FFT size results in PHY dataunits having less subcarriers in each OFDM symbol, thereby resulting inlower data rate and, accordingly, smaller bandwidths occupied by a PHYdata unit generated in VLR mode as compared to PHY data units generatedusing a larger size FFT for the regular mode. As an example, in oneembodiment, the regular mode utilizes FFT of size 64 (or 128, 256, 512,or another suitable size greater than 64), and the VLR mode utilizes FFTsize is 32, 16, or another suitable size less than 64.

Alternatively or additionally, in some embodiments, PHY data units fortransmission in the VLR mode are modulated using a single carrier, whilePHY data units for transmission in regular mode are modulated usingorthogonal frequency domain multiplexing (OFDM) modulation. In some suchembodiments, the VLR mode (single carrier) PHY data units and theregular mode (OFDM) PHY data units are generated using the same clockrate. In some such embodiments, VLR mode PHY data units typically occupya smaller bandwidth compared to the lowest bandwidth occupied by regularmode PHY data units. In an embodiment, in the VLR mode, a single carrierPHY data unit is generated according to the data unit format specifiedby the IEEE 802.11b Standard using a down-clocking ratio of 10 andoccupies a bandwidth that is equal to approximately 1.1 MHz. In otherembodiments, a different suitable down-clocking ratio is used togenerate the VLR mode single carrier PHY data units. For example, thedown-clocking ratio for the VLR mode is specified such that a singlecarrier VLR mode PHY data unit occupies a bandwidth that is equal to acertain desired percentage of the lowest bandwidth occupied by a regularmode OFDM PHY data unit (e.g., ½, ⅔, ¾, etc.). In one embodiment, thesingle carrier down-clocking factor is chosen such that a single carrierPHY data unit in the VLR mode occupies a bandwidth that is approximatelythe same as the bandwidth occupied by the data and pilot tones of alowest bandwidth OFDM PHY data unit transmitted in the regular mode.

A MAC processing unit (such as the MAC processing unit 18 and/or the MACprocessing unit 28) generally provides information to a PHY processingunit (such as the PHY processing unit 20 and/or the PHY processing unit29) for transmission. For example, in an embodiment, the MAC processingunit processes units of information, referred to as MAC service dataunits (MSDUs) and includes the MSDUs in MAC protocol data units (MPDUs).An MPDU includes information from the MSDU along with MAC headerinformation. MPDUs generated by the MAC processing unit are thenprovided to the PHY processing unit. The PHY processing unit includesthe MPDUs in PHY protocol data units (PPDUs) for wireless transmission.A PPDU includes information from the MPDU along with PHY headerinformation.

Similarly, the PHY processing unit receives PPDUs via the wirelessmedium, and extracts MPDUs from the received PPDUs. The PHY processingunit provides the extracted MPDUs to the MAC processing unit, which thenextracts MSDUs from the extracted MPDUs.

FIG. 2 is a diagram illustrating a fragmentation operation that a MACprocessing unit (such as the MAC processing unit 18 and/or the MACprocessing unit 28) is configured to perform, according to someembodiments. A length of an MSDU 204 is compared to a fragmentationthreshold to determine whether the MSDU 204 should be fragmented. Whenthe length of the MSDU 204 exceeds the fragmentation threshold, the MSDU204 is fragmented into two or more fragments 208. Next, the fragments208 are included in respective MPDUs 212, which are provided to the PHYprocessing unit. Each MPDU is included in a respective PPDU by the PHYprocessing unit, in an embodiment.

In an embodiment, the fragmentation threshold is dynamically determinedbased on a current transmission rate. For example, in an embodiment, thefragmentation threshold is dynamically determined based on one or moreof a current MCS being utilized, a current number of spatial orspace-time streams being utilized, a current channel bandwidth beingutilized, etc. In an embodiment, the fragmentation threshold isdynamically determined also based on a retry transmission rate. Forexample, in an embodiment, the fragmentation threshold is dynamicallydetermined based on a lowest retry transmission rate.

In another embodiment, the fragmentation threshold is determined basedon a current mode of operation. For example, when the current mode ofoperation is the regular mode, a first fragmentation threshold isutilized, whereas when the current mode of operation is the VLR mode, asecond fragmentation threshold is utilized, in an embodiment. The firstfragmentation threshold is greater than the second fragmentationthreshold, in an embodiment.

FIG. 3 is a flow diagram of an example method 225 for determiningwhether an MSDU should be fragmented, according to an embodiment. In anembodiment, the method 225 is implemented by a network interface unit(such as the network interface 16 and/or the network interface 27). Forexample, the method 225 is implemented by a MAC processing unit (such asthe MAC processing unit 18 and/or the MAC processing unit 28), in anembodiment.

At block 230, a fragmentation threshold is dynamically determined basedon a current transmission rate. For example, in an embodiment, thefragmentation threshold is dynamically determined based on one or moreof a current MCS being utilized, a current number of spatial orspace-time streams being utilized, a current channel bandwidth beingutilized, etc. In an embodiment, the fragmentation threshold isdynamically determined also based on a retry transmission rate. Forexample, in an embodiment, the fragmentation threshold is dynamicallydetermined based on a lowest retry transmission rate.

At block 234, an MSDU is received. At block 238, it is determinedwhether a length of the MSDU exceeds the fragmentation thresholddetermined at block 230. When it is determined that the length of theMSDU exceeds the fragmentation threshold, the flow proceeds to block242. At block 242, the MSDU is fragmented into multiple MPDUs.

On the other hand, if it is determined at block 238 that the length ofthe MSDU does not exceed the fragmentation threshold, the flow proceedsto block 244. At block 244, the MSDU is entirely included in a singleMPDU.

MPDUs generated according to the method 225 are provided to the PHYprocessing unit, which generates a respective PPDU that includes eachrespective MPDU, in an embodiment.

Referring again to FIG. 2, in an embodiment, different fragmentationthresholds are utilized for the regular mode and the VLR mode. Forexample, in an embodiment, a first fragmentation threshold is utilizedwhile the network interface is transmitting according to the regularmode, whereas a second fragmentation threshold is utilized while thenetwork interface is transmitting according to the VLR mode. In anembodiment, the first fragmentation threshold is larger than the secondfragmentation threshold. In an embodiment, the regular mode of operationincludes a plurality of first possible data rates including a firstlowest possible data rate, and the fragmentation threshold utilized inthe regular mode is based on the first lowest possible data rate.Additionally, in this embodiment, the VLR mode of operation includes aplurality of second possible data rates including a second lowestpossible data rate, and the fragmentation threshold utilized in the VLRmode is based on the second lowest possible data rate.

FIG. 4 is a flow diagram of an example method 250 for determiningwhether an MSDU should be fragmented, according to an embodiment. In anembodiment, the method 250 is implemented by a network interface unit(such as the network interface 16 and/or the network interface 27). Forexample, the method 250 is implemented by a MAC processing unit (such asthe MAC processing unit 18 and/or the MAC processing unit 28), in anembodiment.

At block 254, an MSDU is received. At block 258, it is determinedwhether the current mode of operation is the regular mode. When it isdetermined that the current mode of operation is the regular mode, theflow proceeds to block 262.

At block 262, it is determined whether a length of the MSDU exceeds thefirst fragmentation threshold corresponding to the regular mode asdiscussed above. When it is determined that the length of the MSDUexceeds the first fragmentation threshold, the flow proceeds to block266. At block 266, the MSDU is fragmented into multiple MPDUs. On theother hand, if it is determined at block 262 that the length of the MSDUdoes not exceed the first fragmentation threshold, the flow proceeds toblock 270. At block 270, the MSDU is entirely included in a single MPDU.

When it is determined at block 258, however, that the current mode ofoperation is the VLR mode, the flow proceeds to block 274. At block 274,it is determined whether a length of the MSDU exceeds the secondfragmentation threshold corresponding to the VLR mode as discussedabove. When it is determined that the length of the MSDU exceeds thesecond fragmentation threshold, the flow proceeds to block 278. At block278, the MSDU is fragmented into multiple MPDUs. On the other hand, ifit is determined at block 274 that the length of the MSDU does notexceed the second fragmentation threshold, the flow proceeds to block282. At block 282, the MSDU is entirely included in a single MPDU.

MPDUs generated according to the method 250 are provided to the PHYprocessing unit, which generates a respective PPDU that includes eachrespective MPDU, in an embodiment.

FIG. 5 is a diagram illustrating a fragmentation operation that a MACprocessing unit (such as the MAC processing unit 18 and/or the MACprocessing unit 28) is configured to perform, according to someembodiments. The diagram of FIG. 5 is similar to the diagram of FIG. 2,except that, in some scenarios, fragments of an MSDU are aggregatedwithin an aggregate MPDU (A-MPDU) such as or similar to the A-MPDUdescribed in the IEEE 802.11n Standard.

A length of an MSDU 304 is compared to a fragmentation threshold todetermine whether the MSDU 204 should be fragmented. In an embodiment,the fragmentation threshold is a dynamic fragmentation threshold such asdescribed above. In another embodiment, the fragmentation threshold is amode-dependent fragmentation threshold such as described above. Inanother embodiment, a single fragmentation threshold is utilized in allmodes and/or with all data rates.

When the length of the MSDU 304 exceeds the fragmentation threshold, theMSDU 304 is fragmented into two or more fragments 308. Next, thefragments 308 are included in respective MPDUs 312.

In an embodiment, multiple MPDUs 312 are aggregated within an A-MPDU316, in some scenarios. For example, it is determined whether multipleMPDUs 312 can be aggregated such that a length of the resulting A-MPDUdoes not exceed a maximum A-MPDU length. In the scenario illustrated inFIG. 5, all three MPDUs are capable of being aggregated withoutexceeding the maximum A-MPDU length. In other scenarios, less than allof the MPDUs 312 can be aggregated within a single A-MPDU withoutexceeding the maximum A-MPDU length. The A-MPDU is provided to the PHYprocessing unit, which generates a PPDU that includes the A-MPDU, in anembodiment. If multiple A-MPDUs 316 are generated, each A-MPDU isprovided to the PHY processing unit, which generates a respective PPDUthat includes the respective A-MPDU, in an embodiment.

In an embodiment, the maximum A-MPDU length is dynamically determinedbased on a current transmission rate. For example, in an embodiment, themaximum A-MPDU length is dynamically determined based on one or more ofa current MCS being utilized, a current number of spatial or space-timestreams being utilized, a current channel bandwidth being utilized, etc.In an embodiment, the maximum A-MPDU length is dynamically determinedalso based on a retry transmission rate. For example, in an embodiment,the maximum A-MPDU length is dynamically determined based on a lowestretry transmission rate.

In another embodiment, the maximum A-MPDU length is determined based ona current mode of operation. For example, when the current mode ofoperation is the regular mode, a first maximum A-MPDU length isutilized, whereas when the current mode of operation is the VLR mode, asecond maximum A-MPDU length is utilized, in an embodiment. The maximumA-MPDU length is greater than the second maximum A-MPDU length, in anembodiment.

In another embodiment, aggregation of MSDU fragments is utilized in theregular mode, but is not utilized in the VLR mode.

In an embodiment, only MPDUs 312 corresponding to a single MSDU can beaggregated within an A-MPDU 316. Thus, in some scenarios in which all ofthe MPDUs 312 corresponding to a single MSDU 304 cannot be aggregatedwithin a single A-MPDU 316, some of the MPDUs 312 (e.g., the MPDUs 312 aand 312 b) are included within a single A-MPDU 316, whereas one or moreother MPDUs 312 (e.g., the MPDU 312 c) are provided to the PHYprocessing unit as non-aggregate MPDUs 312. In another embodiment, MPDUs312 corresponding to different MSDUs can be aggregated within an A-MPDU316. In other words, an A-MPDU 316, in some scenarios, contains MPDUs312 corresponding to different MSDUs 304, in an embodiment.

FIG. 6 is a flow diagram of an example method 325 for fragmenting anMSDU, when appropriate, and aggregating multiple MSDU fragments into anA-MPDU, when appropriate, according to an embodiment. In an embodiment,the method 325 is implemented by a network interface unit (such as thenetwork interface 16 and/or the network interface 27). For example, themethod 325 is implemented by a MAC processing unit (such as the MACprocessing unit 18 and/or the MAC processing unit 28), in an embodiment.

At block 330, an MSDU is received. At block 334, the MSDU is fragmentedinto multiple MPDUs when a length of the MSDU exceeds a fragmentationthreshold. At block 338, multiple MPDUs generated at block 334 areaggregated within an A-MPDU when it is determined that the multipleMPDUs 312 can be aggregated such that a length of the resulting A-MPDUdoes not exceed a maximum A-MPDU length.

A-MPDUs generated according to the method 325 are provided to the PHYprocessing unit, which generates a respective PPDU that includes eachrespective A-MPDU, in an embodiment.

In an embodiment, the method 325 is performed in the regular mode ofoperation but is not performed in the VLR mode of operation. In anotherembodiment, the method 325 is performed in both the regular mode ofoperation and the VLR mode of operation.

In embodiments in which fragments of MSDUs are included in one or moreA-MPDUs, various suitable acknowledgment mechanisms are utilized. Forexample, in one embodiment, a receiver generates and transmits anacknowledgment of an A-MPDU when the receiver correctly receives allMPDUs within the A-MPDU. In another embodiment, a receiver generates andtransmits a block acknowledgment of an A-MPDU, where the blockacknowledgment includes (i) a sequence number (SN) corresponding to theMSDU from which the fragments were generated, and (ii) a bitmap toindicate which of the fragments were received correctly. In anotherembodiment, a receiver generates and transmits a block acknowledgment ofone or more A-MPDUs and/or MPDUs, where the block acknowledgmentincludes (i) an SN corresponding to an initial MSDU to which the blockacknowledgment corresponds, and (ii) an SN bitmap to indicate whichentire MSDUs were received correctly.

In some embodiments, a full MPDU MAC header is included in the firstMSDU fragment included in an A-MPDU, whereas other fragments in theA-MPDU have a simplified and/or shortened MAC header to help reduce theoverall length of the A-MPDU. FIG. 7A is a diagram of an example MSDUfragment 350 included in an A-MPDU and that may be utilized for at leastsome MSDU fragments in an A-MPDU, in some embodiments. The fragment 350includes a MAC header portion 354 and a payload 358. In an embodiment,the MAC header portion 354 is shorter than and/or omits fields the MACheader specified in the current IEEE 802.11 Standard. For example, in anembodiment, the MAC header portion 354 includes a fragment number (FN)field and a bit that indicates whether subsequent MSDU fragments follow,but omits one or more of an SN field, a receiving station address (RA)field and a transmitting station address (TA) field.

In some embodiments, MSDU fragments included in an A-MPDU have asimplified and/or shortened MPDU delimiter (as compared to the MPDUdelimiter specified by the IEEE 802.11n Standard) to help reduce theoverall length of the A-MPDU. FIG. 7B is a diagram of an example A-MPDUsubframe 370 (which includes an MSDU fragment) that may be utilized insome embodiments. The subframe 370 includes a delimiter portion 374 andan MPDU 378 (that includes an MSDU fragment). In some embodiments, thedelimiter portion 374 is shorter than and/or omits fields of the A-MPDUdelimiter field specified in the IEEE 802.11n Standard. For example, inan embodiment, the delimiter field 374 has a length of two bytes. Inanother embodiment, the delimiter field 374 has a length of three bytes.In some embodiments, the MPDU 378 has a MAC header that is shorter thanand/or omits fields of the MAC header field specified in the currentIEEE 802.11 Standard. For example, in an embodiment, the SN field of theMPDU has a length of 6 bits. As another example, in an embodiment, theFN field of the MPDU has a length of 2 bits.

In some embodiments, techniques described with respect to FIG. 7A arecombined with techniques described with respect to FIG. 7B in order toreduce the overall length of the A-MPDU.

FIG. 8 is a diagram illustrating a fragmentation operation that a MACprocessing unit (such as the MAC processing unit 18 and/or the MACprocessing unit 28) is configured to perform, as well as an aggregationprocess that a PHY processing unit (such as the PHY processing unit 20and/or the PHY processing unit 2) is configured to perform, according tosome embodiments. The diagram of FIG. 8 is similar to the diagram ofFIG. 5, except that, in some scenarios, fragments of an MSDU areaggregated within an extended PPDU Liked numbered elements from FIG. 5are not discussed in detail for brevity.

The MPDUs 312, which correspond to the fragments of the MSDU 304, areprovided to the PHY processing unit. In an embodiment, multiple MPDUs312 are aggregated, by the PHY processing unit, within an extended PPDU404, in some scenarios. For example, it is determined whether multipleMPDUs 312 can be aggregated such that a length of the resulting extendedPPDU does not exceed a maximum extended PPDU length. In the scenarioillustrated in FIG. 8, all three MPDUs are capable of being aggregatedwithout exceeding the maximum extended PPDU length. In other scenarios,less than all of the MPDUs 312 can be aggregated within a singleextended PPDU without exceeding the maximum extended PPDU length.

In an embodiment, the maximum extended PPDU length is dynamicallydetermined based on a current transmission rate. For example, in anembodiment, the maximum extended PPDU length is dynamically determinedbased on one or more of a current MCS being utilized, a current numberof spatial or space-time streams being utilized, a current channelbandwidth being utilized, etc. In an embodiment, the maximum extendedPPDU length is dynamically determined also based on a retry transmissionrate. For example, in an embodiment, the maximum extended PPDU length isdynamically determined based on a lowest retry transmission rate.

In another embodiment, the maximum extended PPDU length is determinedbased on a current mode of operation. For example, when the current modeof operation is the regular mode, a first maximum extended PPDU lengthis utilized, whereas when the current mode of operation is the VLR mode,a second maximum extended PPDU length is utilized, in an embodiment. Themaximum extended PPDU length is greater than the second maximum extendedPPDU length, in an embodiment.

In other embodiments, it is determined whether multiple MPDUs 312 can beaggregated such that a length of the resulting extended PPDU fits withina transmit opportunity (TXOP) period.

In another embodiment, aggregation of MSDU fragments into an extendedPPDU is utilized in the regular mode, but is not utilized in the VLRmode.

In an embodiment, only MPDUs 312 corresponding to a single MSDU can beaggregated within an extended PPDU 404. Thus, in some scenarios in whichall of the MPDUs 312 corresponding to a single MSDU 304 cannot beaggregated within a single extended PPDU 404, some of the MPDUs 312(e.g., the MPDUs 312 a and 312 b) are included within a single extendedPPDU 404, whereas one or more other MPDUs 312 (e.g., the MPDU 312 c) aretransmitted as regular PPDUs (e.g., non-extended PPDUs). In anotherembodiment, MPDUs 312 corresponding to different MSDUs can be aggregatedwithin an extended PPDU 404. In other words, an extended PPDU 404, insome scenarios, contains MPDUs 312 corresponding to different MSDUs 304,in an embodiment.

FIG. 9A is a diagram of an example extended PPDU 420, according to anembodiment. The extended PPDU 420 includes a plurality of subframes(e.g., subframe 1, subframe 2 and subframe 3 in the illustrative exampleof FIG. 9A). The first subframe of the extended PPDU 420 includes a PHYpreamble 424 with a signal field 428. The signal field 428 includes anindication of the duration of the extended PPDU 420, in an embodiment.The first subframe includes a MAC header (MH) portion 432 and a MAC dataportion 436. Each of the following one or more subframes includes amid-amble 440 and a MAC data portion 444, and omits a MH portion, in anembodiment. The mid-amble 440 is a duplicate of the PHY preamble 424 inan embodiment. The mid-amble 440 includes only a portion of the PHYpreamble 424 in an embodiment (e.g., the mid-amble 440 omits certainsuitable fields of the PHY preamble 424). The mid-amble 440 is a shorterversion of the PHY preamble 424 in an embodiment (e.g., certain suitablefields in the mid-amble 440 are suitably shortened in length as comparedto the corresponding fields of the PHY preamble 424).

The mid-ambles 440 are configured to improve reception of extended PPDUsat least by providing training data to permit receiving stations toupdate a channel estimate during reception of the extended PPDU 420.Additionally, each mid-amble 440 includes a signal field that includesduration information indicating a remaining duration of the extendedPPDU 420, in an embodiment. Such duration information will assistreceiving stations is determining when the extended PPDU 420 will endfor purposes of power saving modes, etc.

In an embodiment, a suitable gap is included between adjacent subframesof the extended PPDU 420. In an embodiment, the gap is at least a shortinterframe space (SIFS) as defined by the IEEE 802.11 Standard, a RIFS,or another suitable spacing.

In various embodiments, the receiving station acknowledges the extendedPPDU 420 with an acknowledgment or a block acknowledgment 448. Forexample, in one embodiment, the receiving station acknowledges theextended PPDU 420 with an acknowledgment 408 only when all of thesubframes of the extended PPDU 420 are received correctly. In anotherembodiment, the receiving station acknowledges the extended PPDU 420with a block acknowledgment 408 that indicates (e.g., with a bitmap)which of the subframes of the extended PPDU 420 were received correctly.

FIG. 9B is a diagram of another example extended PPDU 455, according toanother embodiment. The extended PPDU 455 is similar to the extendedPPDU 420 of FIG. 9A, except that each of the subframes that follows thefirst subframe includes a mid-MAC header (MMH) portion 460.

The MMH portion 460 includes only a portion of the MH portion 432 in anembodiment (e.g., the MMH portion 460 omits certain suitable fields ofthe MH portion 432, such as one or more of an RA field, a TA field, aframe control field, etc.). In an embodiment, the MMH portion 460includes one or more of a SN field, an FN field, a security header, alength field, etc.

The MMH portion 460 is a shorter version of the MH portion 432 in anembodiment (e.g., certain suitable fields in the MMH portion 460 aresuitably shortened in length as compared to the corresponding fields ofthe MH portion 432). For example, in an embodiment, an SN field of theMMH portion 460 has a length of 6 bits. As another example, in anembodiment, an FN field of the MMH portion 460 has a length of 2 bits.

In another embodiment, each MMH portion 460 is a duplicate of the MHportion 432.

Referring now to FIGS. 9A and 9B, in some embodiments, each subframeincludes one or both of (i) a security tail field (e.g., a messageintegrity code (MIC)) and (ii) an error detection information field,such as a frame check sequence (FCS) field, a cyclic redundancy check(CRC) field, etc. In an embodiment, each subframe is self-contained sothat even if one or more subframes are not correctly received, areceiver can still identify correctly received subframes and request thesender to retransmit only the incorrectly received subframes. In anembodiment, each subframe includes a complete MPDU or A-MPDU. In anembodiment, the first subframe includes a complete MPDU, whereassubsequent subframes include fragments of another MPDU.

In another embodiment, each subframe includes a fragment of a fragmentedMPDU. In an embodiment, MMH portions 460 are omitted, such as in theexample format of FIG. 9A. When MMH portions 460 are omitted, the entireMPDU must be retransmitted when even only one fragment is not receivedcorrectly.

In an embodiment, the first subframe includes a complete MAC header fora fragmented MPDU, an FCS field, and a first fragment of the MPDU.Subsequent subframes each include an MMH portion 460 as in FIG. 9B, andFCS field, and a respective fragment of the MPDU. In this embodiment,fragments of the MPDU that were received correctly need not beretransmitted when only some fragments are not received correctly.

In other embodiments, the PHY processing unit transmits multiple closelyspaced PPDUs corresponding to the multiple MPDUs 312, in some scenarios.The closely spaced PPDUs are PPDUs separated only by a short timeperiod, such as the reduced interframe space (RIFS) defined in the IEEE802.11n Standard or another suitable time duration. For example, it isdetermined whether multiple MPDUs 312 can be transmitted as multiplePPDUs such that the multiple PPDUs can be transmitted within a TXOPperiod.

In an embodiment, transmission of MSDU fragments as multiple closelyspaced PPDUs is utilized in both the regular mode and the VLR mode. Inanother embodiment, transmission of MSDU fragments as multiple closelyspaced PPDUs is utilized in the regular mode, but is not utilized in theVLR mode.

FIG. 10 is a flow diagram of an example method 470 for fragmentation andsubsequent aggregation. In an embodiment, the method 470 is implementedby a network interface unit (such as the network interface 16 and/or thenetwork interface 27). For example, in an embodiment, the method 470 isperformed by a MAC processing unit (such as the MAC processing unit 18and/or the MAC processing unit 28) a PHY processing unit (such as thePHY processing unit 20 and/or the PHY processing unit 2).

At block 474, an MSDU is received. At block 478, the MSDU is fragmentedinto multiple MPDUs when a length of the MSDU exceeds a fragmentationthreshold. The MPDUs generated at block 478 are provided to the PHYprocessing unit, which generates, at block 482, an extended PPDU orclosely spaced PPDUs (such as described above) to aggregate the multipleMPDUs generated at block 478 such that the resulting extended PPDU orclosely spaced PPDUs do not exceed a maximum extended PPDU length orTXOP period, in an embodiment.

In an embodiment, the method 470 is performed in the regular mode ofoperation but is not performed in the VLR mode of operation. In anotherembodiment, the method 470 is performed in both the regular mode ofoperation and the VLR mode of operation.

In an embodiment, the method 470 is combined with the method 325 of FIG.6. For example, MPDUs are aggregated into an A-MPDU such as according tothe method 325, and multiple A-MPDUs and/or one A-MPDU with one or moreMPDUs are aggregated into an extended PPDU or closely spaced PPDUs in amanner similar to the method 470.

FIG. 11 is a flow diagram of an example method 500 for formatting dataunits for wireless transmission, according to an embodiment. In anembodiment, the method 500 is implemented by a network interface unit(such as the network interface 16 and/or the network interface 27).

At block 504, it is determined whether the current mode of operation isthe regular mode or the VLR mode. If it is determined that the currentmode of operation is the regular mode, the flow proceeds to block 508.At block 508, a PPDU maximum duration is utilized so that an MPDU havinga maximum length defined by the MAC protocol layer in a protocol stack(e.g., 1500 bytes or another suitable length) will fit entirely within asingle PPDU when transmitting at a lowest possible data rate of theregular mode. Utilizing such a PPDU maximum duration will help reducethe amount of fragmentation required.

On the other hand, if it is determined at block 504 that the currentmode of operation is the VLR mode, the flow proceeds to block 512. Atblock 512, a PPDU maximum duration is utilized so that an MPDU having amaximum length defined by the MAC protocol layer in a protocol stack(e.g., a maximum Ethernet frame size, a maximum frame size determined byanother suitable protocol above the PHY layer in the protocol stack,1500 bytes or another suitable length, etc.) will not fit entirelywithin a single PPDU when transmitting at a lowest possible data rate ofthe VLR mode. In an embodiment, the same PPDU maximum duration isutilized in the regular mode and the VLR mode. In another embodiment,different PPDU maximum durations are utilized in the regular mode andthe VLR mode.

FIG. 12 is a flow diagram of an example method 550 for formatting dataunits for wireless transmission, according to an embodiment. In anembodiment, the method 550 is implemented by a network interface unit(such as the network interface 16 and/or the network interface 27).

At block 554, it is determined whether the current mode of operation isthe regular mode or the VLR mode. If it is determined that the currentmode of operation is the regular mode, the flow proceeds to block 558.At block 558, a first PPDU maximum duration is utilized. On the otherhand, if it is determined at block 554 that the current mode ofoperation is the VLR mode, the flow proceeds to block 562. At block 562,a second PPDU maximum duration is utilized, where the first PPDU maximumduration is different than the second PPDU maximum duration. In anembodiment, the first PPDU maximum duration is less than the second PPDUmaximum duration. In an embodiment, the first PPDU maximum duration is 5ms, whereas the second PPDU maximum duration is greater than 5 ms (e.g.,10 ms, 15 ms, 20 ms, or another suitable duration).

As discussed above, in some embodiments and/or scenarios, a PPDU may belonger than the 5 ms maximum length defined in the current IEEE 802.11Standard. For power save (PS) mode purposes, it is beneficial, at leastin some embodiments, to enable a receiving station to obtain informationquickly about a PPDU being transmitted so that the station can determine(i) whether the station can go back to sleep and/or (ii) for how longthe station can sleep. For example, when a station is in a PS mode, thestation wakes up periodically to listen for beacon frames and/or framesincluding a traffic indication map (TIM) to determine whether anotherstation (e.g., the AP 14) has data buffered for the station, in someembodiments. In another embodiment, the other station (e.g., the AP 14)will not send unicast frames to the station in the PS mode unless theother station (e.g., the AP 14) is first prompted to do so by thestation in the PS mode. Thus, in some embodiments, a station in a PSmode that wakes up and hears a unicast frame and the station knows thatthe station has not yet prompted such a unicast frame, the station inthe PS mode knows that the unicast frame is not intended for thestation. However, the station in the PS mode may want to know theduration of the unicast frame for purposes of (i) going back to sleep,(ii) determining when the station can attempt a transmission, etc. Thus,in some embodiments, information useful (at least in some scenarios) fora station in a PS mode is included in an early portion of a PPDU toenable the station in the PS mode to obtain the information quickly.

FIG. 13 is a flow diagram of an example method 570 for generating PHYdata units for wireless transmission, according to an embodiment. In anembodiment, the method 570 is implemented by a network interface unit(such as the network interface 16 and/or the network interface 27). Forexample, a network interface is configured to implement the method 570.

At block 574, a PPDU maximum duration is utilized so that (A) whenoperating in first mode (e.g., the regular mode), an Ethernet framehaving a maximum length (as specified by a MAC protocol, e.g., the IEEE802.3 Standard) will fit entirely within a single PPDU at a lowestpossible data rate in the first mode, and (B) when operating in a secondmode (e.g., the VLR mode), the Ethernet frame having the maximum lengthwill not fit entirely within a single PPDU at a lowest possible datarate in the VLR mode.

At block 576, MSDUs are received. At block 578, it is determined whetherthe MSDUs are to be transmitted in the first mode (e.g., regular mode)or the second mode (VLR mode). When the MSDUs are to be transmitted inthe second mode, the flow proceeds to block 580. At block 580, MPDUs toinclude the MSDUs are generated. For each MSDU, it is determined whethera length of the MSDU exceeds a fragmentation threshold. When the MSDUlength exceeds the fragmentation threshold, multiple MPDUs are generatedto include different fragments of the MSDU. When the MSDU length doesnot exceed the fragmentation threshold, a single MPDU is generated toinclude the MSDU.

At block 582, PPDUs are generated to include the MPDUs. Each PPDU has aduration less than or equal to the maximum PPDU duration. At block 584,the PPDUs are transmitted, or caused to be transmitted. For example, aPPDU is transmitted according to the first mode when it is determinedthat the first mode is to be utilized, whereas the PPDU is transmittedaccording to the second mode when it is determined that the second modeis to be utilized.

On the other hand, if it is determined at block 578 that the MSDUs areto be transmitted in the first mode (e.g., regular mode), the flowproceeds to block 586. At block 586, MPDUs are generated to include theMSDUs. In an embodiment, block 586 omits comparing MSDU lengths to afragmentation threshold. In another embodiment, block 586 includesfragmentation the same as block 580 except that a different (e.g.,longer) fragmentation threshold is utilized. In other words, block 580may utilize a first fragmentation threshold, whereas block 586 utilizesa second fragmentation threshold that is larger than the firstfragmentation threshold.

The flow proceeds from block 586 to block 582.

In other embodiments, block 574 involves utilizing a PPDU maximumduration that is determined based on maximum length of a data unit otherthan an Ethernet frame, such as a data unit (i) defined by anothersuitable protocol in a layer above the PHY protocol in a protocol stackand (ii) having a maximum length defined by the protocol above the PHYprotocol.

In some embodiments and/or scenarios, the method 570 of FIG. 13 enablesavoiding any fragmentation of MSDUs when operating in the regular mode,whereas fragmentation of MSDUs may still occur when operating in theregular mode.

FIG. 14 is a block diagram of a format for a PPDU 600 with an extendedduration (as compared to the current IEEE 802.11 Standard), according toan embodiment. The PPDU 600 includes a PPDU preamble portion 604, a MACheader portion 608, and a MAC data portion 612. The PHY preamble portion604 includes a signal field 616.

In an embodiment, the signal (SIG) field 616 includes a duration fieldthat indicates a duration of the PPDU 600. When the duration field isincluded in the SIG field 616 rather than in a MAC header, a receiver isable to determine the duration of a transmission more quickly and can goto sleep more quickly, at least in some embodiments, if the receiverdetermines that the receiver does not need to listen to the PPDU 600.

In an embodiment, the signal field includes a response indication fieldthat indicates whether there is to be a response (e.g., anacknowledgment 620) to the PPDU 600 immediately following the PPDU 600.In an embodiment, a receiver can calculate a duration of the response.For example, the receiver assumes a data rate and length of the responseto determine the duration of the response. In an embodiment, thereceiver assumes the data rate of the response to be the same as thedate rate of the PPDU 600, or another suitable data rate. When thereceiver is able to determine if a response will be transmitted and candetermine or estimate the duration of the response, the receiver can goto sleep for period including both the transmission of the PPDU 600 andthe response (e.g., ACK) to the PPDU 600, at least in some embodiments,if the receiver determines that the receiver does not need to listen tothe PPDU 600.

In an embodiment, in the VLR mode, a duration field in the MAC header608 is omitted if only one frame exchange is allowed for each TXOP inthe VLR mode. For example, a receiver can estimate the duration of thePPDU and the response based on the length of the TXOP.

In an embodiment, the signal field 616 includes a field that indicateswhether the PPDU 600 corresponds to a unicast frame. For example, asdiscussed above, a station in a PS mode can ignore unicast frames (atleast in some scenarios) but should listen to group-addressed andbroadcast frames. Thus, at least in some embodiments and/or scenarios,locating the field that indicates whether the PPDU 600 corresponds to aunicast frame in the SIG field 616 allows a receiver to go to sleep morequickly than if the receiver needed to process the MAC header todetermine if the PPDU 600 corresponds to a unicast frame.

In an embodiment, the signal field 616 includes a field that indicateswhether the PPDU 600 is a beacon frame, a TIM frame, and/or a frameincluding a TIM element. For example, station in a PS mode is interestedin at least some scenarios, when waking up, in receiving beacon frames,TIM frames, and/or frames including TIM elements. As another example, astation operating in the regular mode is interested, in at least somescenarios, in beacon frames transmitted in the VLR mode and/or framesincluding TIM elements that were transmitted in the VLR mode. In anotherembodiment, a station operating in the regular mode ignores all PPDUstransmitted in the VLR mode. At least in some embodiments and/orscenarios, locating a field that indicates whether the PPDU 600 a beaconframe, a TIM frame, and/or a frame including a TIM element in the SIGfield 616 allows a receiver to go to sleep more quickly than if thereceiver needed to process the MAC header to determine if the PPDU 600is a beacon frame, a TIM frame, and/or a frame including a TIM element.

In an embodiment, the signal field 616 includes a field that indicateswhether the PPDU 600 is being transmitted to the AP or from the AP. Forexample, a station is interested, in at least some scenarios, in PPDUstransmitted from the AP. Thus, at least in some embodiments and/orscenarios, locating the field that indicates whether the PPDU 600 istransmitted by the AP in the SIG field 616 allows a receiver to go tosleep more quickly than if the receiver needed to process the MAC headerto determine if the PPDU 600 was transmitted by the AP.

In some embodiments, the MAC header 608 is modified to include adestination address (DA) and/or a network identifier (ID) earlier in theMAC header 608 as compared to the MAC header defined by the current IEEE802.11 Standard. For example, a station listening for unicast framesaddressed to the station must process at least a portion of the MACheader 608 to determine if the MAC header includes a DA that correspondsto the station. For example, a DA field immediately follows a framecontrol (FC) field, in an embodiment. As another example, a DA field isthe first field in the MAC header, in another embodiment. In someembodiments and/or scenarios in which the MAC header includes a networkID field, the network ID field immediately follows the DA field, and theDA field is either (i) immediately following the FC field, or (ii) thefirst field in the MAC header. Thus, at least in some embodiments and/orscenarios, locating the DA and/or a network ID earlier in the MAC header608 allows a receiver to go to sleep more quickly than if the receiverneeded to process more of the MAC header to determine the DA and/or thenetwork ID.

A network interface (such as the network interface 16 and/or the networkinterface 27) is configured to generate a PPDU 600, in an embodiment.

FIG. 15 is a flow diagram of an example method 630 for generating PHYdata units for wireless transmission, according to an embodiment. In anembodiment, the method 630 is implemented by a network interface unit(such as the network interface 16 and/or the network interface 27). Forexample, a network interface is configured to implement the method 630.In some embodiments, the method 630 is for generating a PPDU discussedabove with respect to FIG. 14, or another suitable PPDU.

At block 634, a SIG field is generated, wherein the SIG field includesany combination of one or more of the following: (i) a duration field toindicate a length of a PPDU, (ii) a response indication field toindicate whether a response (e.g., an ACK, BA, etc.) will follow thePPDU, (iii) a unicast indication field to indicate whether the PPDUcorresponds to a unicast transmission, (iv) a beacon/TIM indicationfield to indicate whether the PPDU is a beacon frame, a TIM frame,and/or a frame including a TIM element, (v) a field that indicates ofwhether the PPDU is being transmitted by an AP, and (vi) a CRC field.

At block 638, a MAC header is generated such that one or both of (i) aDA field, and (ii) a network ID field occur earlier in the MAC headerthan specified by the current IEEE 802.11 Standard. For example, a DAfield immediately follows an FC field in the MAC header, in anembodiment. As another example, a DA field is the first field in the MACheader, in another embodiment. In some embodiments and/or scenarios inwhich the MAC header includes a network ID field, the network ID fieldimmediately follows the DA field, and the DA field is either (i)immediately following the FC field, or (ii) the first field in the MACheader. In some embodiments, block 638 is omitted.

At block 642, a PHY data unit is generated to include a preamble, a PHYheader having the SIG field generated at block 634. In some embodiments,the PHY data unit is generated to include a PHY payload. In someembodiments, the PHY payload includes the MAC header generated at block638. In some embodiments, the PHY payload includes the MAC header thatis not generated according to block 638. In some embodiments, the PHYdata unit is generated to omit a PHY payload.

At block 646, the PHY data unit is transmitted or caused to betransmitted.

Some broadcast and/or control frames cannot be fragmented, at least insome embodiments. Thus, in various embodiments, various control framesare modified to have shorter durations as compared to similar controlframes described in the current IEEE 802.11 Standard, for example.

For example, in some embodiments, a network interface of a station(e.g., the AP 14), generates beacons having less information as comparedto the beacons described in the current IEEE 802.11 Standard, forexample. In an embodiment, a beacon frame includes certain basic serviceset (BSS) information such as a timestamp, a beacon interval, a serviceset identifier (SSID), etc., but omits other information that isincluded in beacons described in the current IEEE 802.11 Standard, forexample. In an embodiment, the beacon includes recently updated (e.g.,updated since the immediately previous beacon was transmitted, updatedwithin a certain amount of time, etc.) BSS information. In anembodiment, if a number of BSS information elements (IEs) that recentlychanged is large enough so that all of the IEs that recently changedcannot fit within one beacon frame, the network interface may beconfigured to distribute the IEs that recently changed amongst severalbeacon frames. In another embodiment, if a number of BSS informationelements (IEs) that recently changed is large enough so that all of theIEs that recently changed cannot fit within one beacon frame, thenetwork interface may be configured to include in the beacon anindication of changed BSS IEs that prompts stations to poll the AP tocause the AP to transmit the changed BSS IEs in response to the poll.For example, the beacon includes a field that indicates whether BSS IEshave changed and that prompts stations to poll the AP to cause the AP totransmit the changed BSS IEs in response to the poll, in an embodiment.In an embodiment, in response to such a poll, the network interface ofthe AP transmits information that conveys the changed IEs to the pollingstation. In an embodiment, a station polls the AP for informationregarding changed IEs using a probe request frame, and the AP respondsto the probe request frame with a probe response frame, where the proberesponse frame includes the requested information.

In an embodiment, a station new to a BSS transmits a probe request frameto the AP to obtain detailed BSS information from the AP. In response tothe probe request, detailed BSS information is transmitted by the AP ina probe response frame.

In an embodiment, a probe response frame is divided into multiple proberesponse frames (short probe response frames) thus shortening theduration of each probe response frame as compared to a single proberesponse frame. Each short probe response frame includes a field toindicate whether at least one additional probe response frame is tofollow, in an embodiment. In an embodiment, each short probe responseframe includes a SN field to facilitate selective acknowledgment ofshort probe response frames and retransmission of short probe responseframes that were not received correctly. In an embodiment, all of theshort probe response frames are transmitted in response to a singleprobe request frame. In another embodiment, a station transmits multipleprobe request frames to prompt the AP to transmit the multiple shortprobe response frames.

A TIM information element and/or TIM frame is utilized to inform astation whether the AP has buffered data for the station. When there aremany stations in a BSS, the TIM element and/or frame can be very large,and thus a frame including a TIM element or a TIM frame can be verylong, in some situations.

In an embodiment, the TIM information element or TIM frame includes alist of indicators (e.g., a bitmap) that indicates for which stationsthe AP has buffered data. In an embodiment, each indicator in the list(e.g., each bit in the bitmap) corresponds to a group associationidentifier (Group AID), and each Group AID is a group ID for a group ofstations in the BSS. In an embodiment, when a Group AID indicator in theTIM element or TIM frame indicates data is buffered for the indicatedgroup of stations, each station in the group, in response, polls the APto determine whether the AP has data buffered for the station. When anAP receives such a poll, the AP, in response, determines whether thereis data buffered for the station. If there is data buffered for thestation, the AP transmits buffered data the station. In an embodiment,the AP also transmits, along with buffered data, an indication ofwhether the AP has more buffered data for the station. On the otherhand, if the AP determines, in response to a poll from a station, thatthe AP does not have buffered data for the station, the AP transmits anindication that the AP does not have buffered data for the station.

In another embodiment, when an AP receives such a poll, the AP, inresponse, generates a frame that includes the TIM information element,where the TIM information element indicates for which stations the APhas buffered data, and transmits the frame to the group of stations.This is helpful to other stations in the group that have not yettransmitted a poll to the AP. In another embodiment, when an AP receivessuch a poll, the AP, in response, generates a frame that includes theTIM information element, where the TIM information element indicates forwhich stations the AP has buffered data, and transmits the frame as aunicast frame to the polling station. In an embodiment, when anindicator in the TIM information element indicates data is buffered fora particular station, the station, in response, polls the AP to promptthe AP to transmit buffered data buffered to the station.

In another embodiment, when an AP receives such a poll, the AP, inresponse, generates a frame that includes a segment of TIM informationelement, where the segment of the TIM information element includesinformation that indicates for which stations in the group the AP hasbuffered data, and transmits the frame to the group of stations. This ishelpful to other stations in the group that have not yet transmitted apoll to the AP. In another embodiment, when an AP receives such a poll,the AP, in response, generates a frame that includes a segment of TIMinformation element, where the segment of the TIM information elementincludes information that indicates for which stations in the group theAP has buffered data, and transmits the frame to the polling station. Inan embodiment, when an indicator in the segment of the TIM informationelement indicates data is buffered for a particular station, thestation, in response, polls the AP to prompt the AP to transmit buffereddata buffered to the station.

In another embodiment, the TIM information element is segmented anddistributed amongst multiple beacon frames, TIM frames, etc. In anembodiment, each TIM segment includes information that enables areceiving station to determine when a segment corresponding to thestation will be transmitted. Thus, in an embodiment, when a station in aPS mode wakes up and receives a TIM segment, the station usesinformation in the received TIM segment to determine when another TIMsegment corresponding to the station will be transmitted. The stationcan then go back to sleep until an appropriate time when the other TIMsegment corresponding to the station will be transmitted.

In another embodiment, both (i) a TIM information element withindications of Group AIDs for which the AP has buffered data (a GroupTIM) and (ii) segmented TIM information elements (a segmented TIM) aretransmitted by the AP. In an embodiment, a station first checks theGroup TIM in an attempt to determine whether the AP has data bufferedfor the station. If the station can determine, based on the Group TIM,that the AP does not have data buffered for the station, the station cango back to sleep without checking the segmented TIM. If the stationcannot determine, based on the Group TIM, whether the AP has databuffered for the station, the station then analyzes an appropriate TIMsegment to determine whether the AP has data buffered for the station.

In an embodiment in which a single AP supports multiple basic serviceset identifiers (BSSIDs), a station new to a BSS transmits a proberequest frame to the AP to obtain completed multiple BSSID informationfrom the AP.

In an embodiment in which a single AP supports BSSIDs, if one or moremultiple non-transmitted BSSID (e.g., virtual APs for which separatebeacons are not transmitted) profiles have changed information, the APdistributes the updated BSS information in multiple beacon frames. Inanother embodiment in which a single AP supports BSSIDs, if one or moremultiple non-transmitted BSSID profiles have changed information, the APgenerates a frame (e.g., a beacon frame) with an indicator of changedBSS information, and transmits the frame to stations of one or morecorresponding BSSIDs to prompt the stations to send probes to the AP toobtain the changed BSS information. For example, the indictor is a BSSupdate field that indicates whether BSS information updates areavailable for each non-transmitted BSSID, in an embodiment. As anotherexample, the indictor is a BSS update field that indicates whether BSSinformation updates are available for each transmitted andnon-transmitted BSSID, in an embodiment.

In some embodiments, one or more error detection information fields areincluded in a frame (e.g., a data frame, a management frame, a beaconframe, etc.) to enable receiving stations to verify relevant fields andskip other fields if not needed (e.g., to allow a station to go to sleepsooner for power saving). FIG. 16 is a diagram of an example beaconframe 650 according to an embodiment. A network interface (such as thenetwork interface 16) is configured to generate the beacon frame 650, inan embodiment.

The beacon frame 650 includes a MAC header 654 and a CRC field 658. TheCRC field 658 is generated using the MAC header 654 so that a receivercan utilize the CRC field 658 to verify the integrity of the MAC header654 and analyze information in the MAC header 654 without having toprocess other later portions of the beacon frame 650. Thus, in somesituations, a receiving station can stop processing the remainder of theframe 650 when it determines, after analyzing the MAC header 654, thatthe frame 650 is not intended for the station. For example, if areceiving station determines that a DA address in the MAC header 654does not correspond to the receiving station, the receiving station maystop processing the remainder of the frame 650.

The beacon frame 650 also includes a check updates field 662, atimestamp field 668, a TIM field 672 and a CRC field 676. The CRC field676 is generated using the check updates field 662, the timestamp field668, and the TIM field 672 so that a receiver can utilize the CRC field676 to verify the integrity of the check updates field 662, thetimestamp field 668, and/or the TIM field 672, and analyze informationin the check updates field 662, the timestamp field 668, and/or the TIMfield 672 without having to process other portions of the beacon frame650. Thus, in some situations, a receiving station can stop processingthe remainder of the frame 650 when it determines, after analyzing thecheck updates field 662, the timestamp field 668, and/or the TIM field672, that the station does not need to further process the frame 650.For example, if a receiving station determines, from the TIM field 672,that the AP does not have buffered data for the station, the receivingstation may stop processing the remainder of the frame 650.

The beacon frame 650 also includes other fields and/or elements 680 andan FCS field 684. In an embodiment, the FCS field 684 is generated usingthe fields 680 and without using one or more of the MAC header 654, theCRC 658, the check updates field, the TIM field 672 or the CRC field676. In another embodiment, the FCS field 684 is generated using the MACheader 654, the CRC 658, the check updates field, the TIM field 672 theCRC field 676, and the other fields 680.

In an embodiment, the CRC field 658 is omitted. In an embodiment inwhich the CRC field 658 is omitted, the CRC field 676 is generated usingthe MAC header field 654. In another embodiment, the CRC field 676 isomitted.

In embodiments in which a network interface decides to stop furtherprocessing of the frame 650, the network interface may enter a sleepmode for the remainder of the frame 650 to reduce energy consumption.

In some embodiments, a beacon frame has a shorter length as compared tobeacon frames defined by the current IEEE 802.11 Standard. FIG. 17 is adiagram of an example beacon frame 700 according to an embodiment. Anetwork interface (such as the network interface 16) is configured togenerate the beacon frame 700, in an embodiment.

The beacon frame 700 includes a frame control field 704, a sourceaddress (SA) field, a compressed SSID field 712, a timestamp field 716,a change sequence field 720, a BSS information field 724, an IE payloadfield 728, and an FCS field 732. The beacon payload field 728 includesinformation elements (IEs) such as a TIM IE 736. In an embodiment, theTIM IE 736 is the first IE in the IE payload field 728. In anembodiment, the compressed SSID field 712 contains a compressed versionof a full SSID (as defined in the current IEEE 802.11 Standard). In anembodiment, the compressed SSID field 712 includes a concatenatedversion (e.g., less bits) of the full SSID. In other embodiments, othercompression techniques are utilized.

Often, an associated station checks only certain fields of the beaconframe 700 to determine whether (i) the station should check other fieldsof the beacon frame 700, or (ii) the station can ignore the remainingportions of the beacon frame 700. For example, a station may need tocheck one or more of (i) the timestamp field 716, (ii) the changesequence field 720 (which indicates whether BSS information has changedand thus whether the station should process other fields of the beaconframe 700 to determine what BSS information has changed), or (iii) theTIM IE 736. The beacon frame 700 is formatted such that all fields priorto each of (i) the timestamp field 716, (ii) the change sequence field720, and (iii) the TIM IE 736 are fixed-length fields. This simplifiesparsing of (i) the timestamp field 716, (ii) the change sequence field720, and (iii) the TIM IE 736 in the beacon frame 700. On the otherhand, variable length fields make field location and/or parsing moredifficult and/or more complicated.

In another embodiment, the timestamp field 716 is located immediatelyfollowing the SA field 708.

In another embodiment, device discovery information is included in theBSS info field 724 or as an IE in the IE payload field 728. In anotherembodiment, service discovery information is included in the BSS infofield 724 or as an IE in the IE payload field 728.

FIG. 18 is a diagram of another example beacon frame 750 according toanother embodiment. A network interface (such as the network interface16) is configured to generate the beacon frame 750, in an embodiment.The beacon frame 750 is similar to the beacon frame 700 of FIG. 17, andlike-numbered elements are not discussed in detail.

The beacon frame 750 includes a frame control field 754, which includesa TIM IE indicator subfield 758 and an SSID IE indicator subfield 762.The TIM IE indicator subfield 758 indicates whether a TIM IE is presentin the beacon frame 750. Similarly, the SSID IE indicator subfield 762indicates whether an SSID IE is present in the beacon frame 750.

The beacon frame 750 also includes a hashed SSID field 766. In anembodiment, a hashing function is applied to a full SSID (e.g., asspecified in the current IEEE 802.11 Standard) to generate the hashedSSID 766.

The beacon frame 750 also includes an IE payload field 770. In anembodiment, the TIM IE 736, when present, is the first IE in the IEpayload field 770. In an embodiment, an SSID IE 774, when present, isthe first IE in the IE payload field 770 when the IE payload field 770does not include the TIM IE 736. The SSID IE 774 includes the full SSID,in an embodiment. In an embodiment, the SSID IE 774 immediately followsthe TIM IE 736, when both the SSID IE 774 and the TIM IE 736 arepresent. In another embodiment, the order of the SSID IE 774 and the TIMIE 736 are reversed. In an embodiment, the TIM IE indicator subfield 758indicates whether the TIM IE 736 is present in the IE payload 770, andthe SSID IE indicator subfield 762 indicates whether the SSID IE 774 ispresent in the IE payload 770.

Similar to the beacon frame 700, the beacon frame 750 is formatted suchthat all fields prior to each of (i) the timestamp field 716, (ii) thechange sequence field 720, and (iii) the TIM IE 736, when present, arefixed-length fields. This simplifies parsing of (i) the timestamp field716, (ii) the change sequence field 720, and (iii) the TIM IE 736 in thebeacon frame 750. On the other hand, variable length fields make fieldlocation and/or parsing more difficult and/or more complicated.

In another embodiment, the timestamp field 716 is located immediatelyfollowing the SA field 708.

In another embodiment, device discovery information is included in theBSS info field 724 or as an IE in the IE payload field 770. In anotherembodiment, service discovery information is included in the BSS infofield 724 or as an IE in the IE payload field 770.

FIG. 19 is a diagram of another example beacon frame 800 according toanother embodiment. A network interface (such as the network interface16) is configured to generate the beacon frame 800, in an embodiment.The beacon frame 800 is similar to the beacon frame 700 of FIG. 17, andlike-numbered elements are not discussed in detail.

The beacon frame 800 includes a mandatory portion 802 that includesfields that are included in the beacon frame 800 in all situations. Inan embodiment, the mandatory portion 802 includes fields that are likelyimportant to stations in many circumstances. The mandatory portion 802is positioned at the beginning of the beacon frame 800 and includesfixed-length fields at fixed positions to simplify and enable quickparsing of the fields in the mandatory portion 802. In an embodiment,the mandatory portion 802 includes a frame control field 804, the SAfield 708, the timestamp field 716, the change sequence field 720 andthe BSS information field 724.

In an embodiment, following the mandatory portion 802, the beacon frame800 includes one or more optional fields that may be omitted in somescenarios. For example, the beacon frame 800 includes a shortened SSIDfield 804 and an interval to next full beacon field 808, at least insome circumstances. The frame control field 804 includes at least someindications of which optional fields are included in the beacon frame800. For example, the frame control field 804 includes a subfield 812that indicates whether the shortened SSID field 804 is present in thebeacon frame 800, in an embodiment. Also, the frame control field 804includes a subfield 816 that indicates whether the interval to next fullbeacon field 808 is present in the beacon frame 800, in an embodiment.In an embodiment, the optional fields are located after the mandatoryportion 802 and prior to the IE payload 728.

In an embodiment, the shortened SSID (e.g., as compared to the full SSIDspecified in the current IEEE 802.11 Standard) is a concatenated versionof the full SSID field, a hashed version of the full SSID, etc.

Similar to the beacon frame 700 and the beacon frame 750, the beaconframe 800 is formatted such that all fields prior to each of (i) thetimestamp field 716, (ii) the change sequence field 720, and (iii) theTIM IE 736, when present, are fixed-length fields. This simplifiesparsing of (i) the timestamp field 716, (ii) the change sequence field720, and (iii) the TIM IE 736 in the beacon frame 800.

FIG. 20 is a diagram of another example beacon frame 850 according toanother embodiment. A network interface (such as the network interface16) is configured to generate the beacon frame 800, in an embodiment.The beacon frame 850 is similar to the beacon frame 800 of FIG. 19, andlike-numbered elements are not discussed in detail.

The beacon frame 850 is similar to the beacon frame 800 of FIG. 19except for several differences. For example, the BSS information hasbeen moved to a subfield 854 within a frame control field 858.Additionally, the order of the fields 804 and 808 has been changed.Similarly, the order of the subfields 812 and 816 has been changed.

In another embodiment, the BSS information is included in the IE payload728. In another embodiment, a first subset of BSS information isincluded in the mandatory portion 802, and a second subset of BSSinformation is included after the mandatory portion and prior to the IEpayload 728. In another embodiment, a first subset of BSS information isincluded in the mandatory portion 802, and a second subset of BSSinformation is included in the IE payload 728.

FIG. 20 is a diagram of another example beacon frame 900 according toanother embodiment. A network interface (such as the network interface16) is configured to generate the beacon frame 800, in an embodiment.The beacon frame 900 is similar to the beacon frame 850 of FIG. 20, andlike-numbered elements are not discussed in detail.

The beacon frame 900 includes support for HotSpot 2.0 (HS 2.0), which isa standard to facilitate seamless mobile handset handoffs betweencellular and Wi-Fi networks. For example, the beacon frame 900 includesoptional fields for including important HS 2.0 information to helpclient stations to discover and select desired APs quickly.

The beacon frame 900 includes a mandatory portion 902, which includes aframe control field 904. Additionally, the beacon 900 includes anoptional field 908 (Short NetID 908) that can be interpreted severaldifferent ways. For example, the Short NetID 908 can be interpreted as ashortened SSID field or a field that provides HS 2.0 information, asdiscussed below.

The frame control field 904 includes a NetID control field 912, whichindicates (i) whether the Short NetID 908 is present in the beacon frame900, and (ii) if present, how the Short NetID 908 is to be interpreted,in an embodiment. Table 3 is shows how the NetID control field 912 isutilized to interpret the Short NetID 908, in an embodiment.

TABLE 3 Interpretation of NetID Control Short NetID 908 00 Not present01 Shortened SSID 10 Hashed SSID 11 HS 2.0 Information

FIG. 21 illustrates the Short NetID 908 interpreted as HS 2.0information. The Short NetID 908 includes an access network optionsfield 916 and a roaming consortium organizationally unique identifier(OUI) field 920.

FIG. 22 is a diagram of another example beacon frame 1000 according toanother embodiment. A network interface (such as the network interface16) is configured to generate the beacon frame 800, in an embodiment.The beacon frame 1000 is similar to the beacon frame 900 of FIG. 21, andlike-numbered elements are not discussed in detail.

The beacon frame 1000 includes a mandatory portion 1002, which includesa frame control field 1004. Additionally, the beacon frame 1000 includesan optional short SSID field 1008 and an optional HS 2.0 informationfield 1012. In an embodiment, the short SSID field 1008 can beinterpreted as a shortened SSID field or a hashed SSID field.

The frame control field 1004 includes a short SSID control field 1016,which indicates (i) whether the short SSID field 1008 is present in thebeacon frame 1000, and (ii) if present, how the short SSID field 1008 isto be interpreted, in an embodiment. The frame control field 1004 alsoincludes an HS 2.0 information present subfield 1020 which indicateswhether the HS 2.0 information field 1012 is present in the beacon 1000.

In an embodiment, the HS 2.0 field includes an advertising protocol IDfield 1024. In another embodiment, the HS 2.0 field omits theadvertising protocol ID field 1024.

FIG. 23 is a diagram of another example beacon frame 1100 according toanother embodiment. A network interface (such as the network interface16) is configured to generate the beacon frame 800, in an embodiment.The beacon frame 1100 is similar to the beacon frame 1000 of FIG. 22,and like-numbered elements are not discussed in detail.

The beacon frame 1100 includes a mandatory portion 1102, which includesa frame control field 1104. Additionally, the access network optionsfield 916 has been moved to the mandatory portion 1102.

The roaming consortium 920 field, when present, and the advertisingprotocol ID field 1024, when present, have been moved to the IE payload728. Additionally, an optional interworking element field 1112 isincluded in the IE payload 728, in an embodiment.

Control frames such as acknowledgments (ACKs), block acknowledgments(BAs), request-to-send (RTS), clear-to-send (CTS), power save polls(PS-Polls), etc., are frequently utilized and thus consume a significantamount of transmission time that may otherwise be available fortransmission of user information. Thus, control frames are a source ofprotocol overhead. Several example techniques, according to variousembodiments, for reducing the duration of control frames are disclosedbelow.

Much of the information carried in prior art SIG fields and/or PHYheaders, and some of the information in prior art MAC headers is notneeded for control frames. In embodiments described below, portions ofthe SIG field and/or PHY header are reused and/or reinterpreted to carryMAC header and/or MAC payload information.

In some embodiments control frames are transmitted using a predefinedand/or fixed PHY parameters (e.g., using binary phase shift keying(BPSK) and/or a single spatial stream).

FIG. 24 is a diagram of an example control frame 1200 that omits a PHYpayload portion. In an embodiment, a network interface unit (such as thenetwork interface 16 and/or the network interface 27) is configured togenerate and transmit the control frame 1200 (or cause the control frame1200 to be transmitted).

The control frame 1200 includes a preamble having one or more shorttraining fields (STFs) 1204, one or more long training fields (LTFs)1208. The control frame 1200 also includes a PHY header having a SIGfield 1212. In an embodiment, each STF field 1204 corresponds to 2 OFDMsymbols. In an embodiment, each LTF field 1208 corresponds to two OFDMsymbols. In various embodiments and/or scenarios, the SIG field 1212corresponds to two, or three, for four OFDM symbols, and has a length ina range of 48 to 96 bits.

In an embodiment, the preamble is configured to indicate that the frame1200 is a control frame. For example, a modulation of the preamble isrotated as compared to other types of frames to indicate that the frame1200 is a control frame, in an embodiment. As another example, aspreading sequence for code is different as compared to other types offrames to indicate that the frame 1200 is a control frame, in anembodiment.

In an embodiment, the SIG field 1212 includes a frame control (FC)/typesubfield 1216, a receiver address (RA) subfield 1220, a transmitteraddress (TA) subfield 1224, a network ID subfield 1228, a durationsubfield 1232, a CRC subfield 1236, and a tail and/or padding subfield1240. Example lengths of the various subfields are shown in FIG. 24. Insome embodiments and/or scenarios, one or more of the TA subfield 1224,the network ID subfield 1228, the duration subfield 1232, and/or thetail/padding subfield 1240 are omitted. In an embodiment the RA subfield1220 includes an AID. In an embodiment the TA subfield 1220 includes anAID. In an embodiment, the network ID subfield 1228 includes a shortenedversion of a BSSID. For example, in an embodiment, the shortened versionof the BSSID is unique in a neighborhood of the BSS. In someembodiments, the RA and/or TA subfields are shortened and/or compressedas compared to RA/TA MAC header fields specified by the current IEEE802.11 Standard.

FIG. 25 is a flow diagram of an example method 1300 for generating acontrol frame for wireless transmission, wherein the control frame omitsa PHY payload portion, according to an embodiment. In an embodiment, themethod 1300 is implemented by a network interface unit (such as thenetwork interface 16 and/or the network interface 27). For example, anetwork interface is configured to implement the method 1300. In someembodiments, the method 1300 is for generating a control frame discussedabove with respect to FIG. 24, or another suitable control frame thatomits a PHY payload portion.

At block 1304, a SIG field is generated, wherein the SIG field includesany combination of one or more of a frame control field, an RA field, aTA field, a network ID field, a duration field, and a CRC field. The SIGfield is generated as discussed above with respect to FIG. 24, in someembodiments.

At block 1308, a PHY preamble is generated. In an embodiment, thepreamble is configured to indicate that the frame is a control frame.For example, a modulation of the preamble is rotated as compared toother types of frames to indicate that the frame is a control frame, inan embodiment. As another example, a spreading sequence for code isdifferent as compared to other types of frames to indicate that theframe is a control frame, in an embodiment.

At block 1312, a control frame that omits a PHY payload portion (an NDPframe) is generated to include (i) the PHY preamble generated at block1308 and (ii) a PHY header having the SIG field generated at block 1304.

At block 1316, the PHY data unit is transmitted or caused to betransmitted.

FIG. 26 is a diagram of an example shorted control frame 1400, accordingto an embodiment. In an embodiment, a network interface unit (such asthe network interface 16 and/or the network interface 27) is configuredto generate and transmit the control frame 1400 (or cause the controlframe 1400 to be transmitted).

The control frame 1400 includes a preamble having one or more shorttraining fields (STFs) 1404, one or more long training fields (LTFs)1408. The control frame 1200 also includes a PHY header having a SIGfield 1412. In an embodiment, each STF field 1404 corresponds to 2 OFDMsymbols. In an embodiment, each LTF field 1408 corresponds to two OFDMsymbols. In an embodiment, the SIG field 1412 corresponds to two OFDMsymbols, and has a length of 48 bits. In other embodiments, each STFfield 1404, each LTF field 1408, and the SIG field 1412 have othersuitable lengths.

The control frame 1400 also includes a PHY data payload portion 1416. Inan embodiment, the control frame 1400 also includes a tail/paddingportion 1420. In some embodiments and/or scenarios, the tail/paddingportion 1420 is omitted.

In an embodiment, the SIG field 1212 includes a subfield 1424 toindicate whether the frame 1400 is a control frame. Additionally, theSIG field 1212 includes a frame control (FC)/type subfield 1216, areceiver address (RA) subfield 1220, a first network ID subfield 1436, aservice subfield 1440, a CRC subfield 1444, and a tail and/or paddingsubfield 1448. Example lengths of the various subfields are shown inFIG. 24, although other suitable lengths are utilized in otherembodiments. In some embodiments and/or scenarios, one or more of thefirst network ID subfield 1436, the service field 1440, and/or thetail/padding subfield 1448 are omitted.

In an embodiment the RA subfield 1220 includes an AID. In an embodiment,the first network ID subfield 1436 includes at least a first portion ofa BSSID. In another embodiment, the first network ID subfield 1436includes at least a first portion of a shortened version of a BSSID. Forexample, in an embodiment, the shortened version of the BSSID is uniquein a neighborhood of the BSS.

The data payload portion 1416 includes a service subfield 1452, aduration subfield 1456, a transmitter address (TA) subfield 1460, asecond network ID subfield 1464, and a CRC subfield 1468. In someembodiments and/or scenarios, one or more of the service field 1452, theTA subfield 1460, and/or the second network ID subfield 1464 areomitted. For example, when the service field 1440 is included in the SIGfield 1412, the service field 1452 is omitted. Similarly, when theservice field 1452 is included, the service field 1440 is omitted fromthe SIG field 1412.

In an embodiment, the TA subfield 1460 includes an AID.

In some embodiments, the RA and/or TA subfields are shortened and/orcompressed as compared to RA/TA MAC header fields specified by thecurrent IEEE 802.11 Standard.

FIG. 27 is a flow diagram of an example method 1500 for generating ashortened control frame for wireless transmission, according to anembodiment. In an embodiment, the method 1500 is implemented by anetwork interface unit (such as the network interface 16 and/or thenetwork interface 27). For example, a network interface is configured toimplement the method 1500. In some embodiments, the method 1500 is forgenerating a control frame discussed above with respect to FIG. 26, oranother suitable shortened control frame.

At block 1504, a SIG field is generated, wherein the SIG field includesa subfield to indicate that the frame is a control frame. Additionally,the SIG field is generated to include any combination of one or more ofa frame control field, an RA field, a first network ID field, a servicefield, and a CRC field. The SIG field is generated as discussed abovewith respect to FIG. 26, in some embodiments.

At block 1508, a PHY payload portion is generated, wherein the PHYpayload portion is generated to include any combination of one or moreof a service subfield, a duration subfield, a TA subfield, a secondnetwork ID subfield, and a CRC field. The PHY payload portion isgenerated as discussed above with respect to FIG. 26, in someembodiments. In an embodiment, the PHY payload portion is generated toomit at least an RA field.

At block 1512, a control frame is generated to include (i) a PHYpreamble, (ii) a PHY header having the SIG field generated at block1504, and (iii) the PHY payload portion generated at block 1508.

At block 1516, the control frame is transmitted or caused to betransmitted.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. Also, some of the variousblocks, operations, and techniques may be performed in a different order(and/or concurrently) and still achieve desirable results. Whenimplemented utilizing a processor executing software or firmwareinstructions, the software or firmware instructions may be stored in anycomputer readable memory such as on a magnetic disk, an optical disk, orother storage medium, in a RAM or ROM or flash memory, processor, harddisk drive, optical disk drive, tape drive, etc. Likewise, the softwareor firmware instructions may be delivered to a user or a system via anyknown or desired delivery method including, for example, on a computerreadable disk or other transportable computer storage mechanism or viacommunication media. Communication media typically embodies computerreadable instructions, data structures, program modules or other data ina modulated data signal such as a carrier wave or other transportmechanism. The term “modulated data signal” means a signal that has oneor more of its characteristics set or changed in such a manner as toencode information in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, radiofrequency, infrared and other wireless media. Thus, the software orfirmware instructions may be delivered to a user or a system via acommunication channel such as a telephone line, a DSL line, a cabletelevision line, a fiber optics line, a wireless communication channel,the Internet, etc. (which are viewed as being the same as orinterchangeable with providing such software via a transportable storagemedium). The software or firmware instructions may include machinereadable instructions that, when executed by the processor, cause theprocessor to perform various acts.

When implemented in hardware, the hardware may comprise one or more ofdiscrete components, an integrated circuit, an application-specificintegrated circuit (ASIC), etc.

While the present invention has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe invention.

What is claimed is:
 1. A method, comprising: dynamically determining, ata network interface, a fragmentation threshold based on a currenttransmission rate; receiving a medium access control (MAC) service dataunit (MSDU); determining, at the network interface, that a length of theMSDU exceeds the fragmentation threshold; fragmenting, at the networkinterface, the MSDU into at least a first MAC protocol data unit (MPDU),a second MPDU, and a third MPDU; aggregating, at the network interface,at least the first MPDU and the second MPDU into a first aggregate MPDU(A-MPDU); generating, at the network interface, a first physical layerprotocol data unit (PPDU) that includes the first A-MPDU, the first PPDUfor transmission via a communication channel; including, at the networkinterface, at least the third MPDU in a second A-MPDU; and generating,at the network interface, a second PPDU that includes the second A-MPDU,the second PPDU for transmission via the communication channel.
 2. Themethod of claim 1, wherein dynamically determining the fragmentationthreshold comprises determining the fragmentation threshold based atleast on a current modulation coding scheme (MCS) being utilized fortransmission.
 3. The method of claim 1, wherein dynamically determiningthe fragmentation threshold comprises determining the fragmentationthreshold based at least on a current number of spatial streams beingutilized for transmission.
 4. An apparatus comprising: a networkinterface having one or more integrated circuits configured todynamically determine a fragmentation threshold based on a currenttransmission rate, determine that a length of a medium access control(MAC) service data unit (MSDU) exceeds the fragmentation threshold,fragment the MSDU into at least a first MAC protocol data unit (MPDU), asecond MPDU, and a third MPDU, aggregate at least the first MPDU and thesecond MPDU into a first aggregate MPDU (A-MPDU); generate a firstphysical layer protocol data unit (PPDU) that includes the first A-MPDU,the first PPDU for transmission via a communication channel; include atleast the third MPDU in a second A-MPDU, and generate a second PPDU thatincludes the second A-MPDU, the second PPDU for transmission via thecommunication channel.
 5. The apparatus of claim 4, wherein the one ormore integrated circuits are configured to determine the fragmentationthreshold based at least on a current modulation coding scheme (MCS)being utilized by the network interface for transmission.
 6. Theapparatus of claim 4, wherein the one or more integrated circuits areconfigured to dynamically determine the fragmentation threshold based atleast on a current number of spatial streams being utilized by thenetwork interface for transmission.
 7. A method, comprising: receiving amedium access control (MAC) service data unit (MSDU); determining, at anetwork interface, that a length of the MSDU exceeds a fragmentationthreshold, wherein the fragmentation threshold is based on a currenttransmission rate; fragmenting, at the network interface, the MSDU intoat least a first MAC protocol data unit (MPDU), a second MPDU, and athird MPDU; aggregating, at the network interface, at least the firstMPDU and the second MPDU into a first aggregate MPDU (A-MPDU);generating, at the network interface, a first physical layer protocoldata unit (PPDU) that includes the first A-MPDU, the first PPDU fortransmission via a communication channel; including, at the networkinterface, at least the third MPDU in a second A-MPDU; and generating,at the network interface, a second PPDU that includes the second A-MPDU,the second PPDU for transmission via the communication channel.
 8. Themethod of claim 7, wherein the first A-MPDU includes one or more MPDUscorresponding to another MSDU.
 9. The method of claim 7, furthercomprising: dynamically determining, at the network interface, thefragmentation threshold based on i) the current transmission rate andii) the width, in frequency, of the communication channel via which thepacket is to be transmitted.
 10. An apparatus comprising: a networkinterface having one or more integrated circuits configured to determinethat a length of a medium access control (MAC) service data unit (MSDU)exceeds a fragmentation threshold, wherein the fragmentation thresholdis based on a current transmission rate, fragment the MSDU into multipleMAC protocol data unit (MPDU), a second MPDU, and a third MPDU,aggregate at least the first MPDU and the second MPDU into a firstaggregate MPDU (A-MPDU); generate a first physical layer protocol dataunit (PPDU) that includes the first A-MPDU, the first PPDU fortransmission via a communication channel, include at least the thirdMPDU in a second A-MPDU, and generate a second PPDU that includes thesecond A-MPDU, the second PPDU for transmission via the communicationchannel.
 11. The apparatus of claim 10, wherein the first A-MPDUincludes one or more MPDUs corresponding to another MSDU.
 12. Theapparatus of claim 10, wherein the one or more integrated circuits areconfigured to: dynamically determine the fragmentation threshold basedon i) the current transmission rate and ii) the width, in frequency, ofthe communication channel via which the packet is to be transmitted.